共线铁磁体中Edelstein效应与自旋轨道转矩的自旋群理论
Spin-group theory on Edelstein effect and spin-orbit torque in Collinear Ferromagnets
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中文总结 AI 辅助
本文建立共线铁磁体中Edelstein效应与自旋轨道转矩的自旋群对称性理论，推导转矩形式并揭示SOC作用，其预测与第一性原理计算高度吻合，为相关现象提供统一对称框架。
中文摘要 AI 辅助
电流诱导的自旋轨道转矩（SOT）是自旋电子器件中磁序电操控的核心。在过渡金属/共线铁磁体双层膜中，类场转矩与类阻尼转矩仅通过自旋或轨道霍尔效应得到唯象描述，缺乏严格的基于对称性的基础。自旋轨道耦合（SOC）在Edelstein效应和SOT中的精确作用仍未明确。本文中，我们将SOC视为对称性破缺微扰，建立了共线铁磁体中Edelstein效应与SOT的自旋群对称性理论。对于4mm（C4v）点群对称性，我们推导了类场转矩与类阻尼转矩的完整形式，二者主要源自一阶SOC与二阶SOC。我们进一步证明，轨道霍尔主导的Ti/Ni双层膜与自旋霍尔主导的Pt/CoFe双层膜中的SOT均起源于一阶SOC。以3m（C3v）转矩为范例，我们阐明了二阶及更高阶SOC转矩在垂直磁各向异性的无场翻转中的作用。值得注意的是，在PtMnSb中，我们证明某些点群对称性下的SOT偏离常规形式：零阶与一阶SOC贡献完全消失，主导SOT源自二阶项。自旋群理论的所有基于对称性的预测与第一性原理计算在定量上高度吻合。本研究为铁磁体系中Edelstein效应与电流诱导自旋转矩的微观理解建立了统一的对称性框架。
英文摘要
Current-induced spin-orbit torques (SOTs) are central to the electrical manipulation of magnetic order in spintronic devices. In transition-metal/collinear ferromagnet bilayers, field-like and damping-like torques have been described only phenomenologically via the spin or orbital Hall effect, lacking a rigorous symmetry-based foundation. The precise role of spin-orbit coupling (SOC) in both the Edelstein effect and SOTs has remained unresolved. Here we develop a spin-group symmetry theory for the Edelstein effect and SOTs in collinear ferromagnets, treating SOC as a symmetry-breaking perturbation. For 4mm (C4v) point group symmetry, we derive the full forms of field-like and damping-like torques, which arise predominantly from first- and second-order SOC. We further show that SOTs in both orbital-Hall-dominated Ti/Ni and spin-Hall-dominated Pt/CoFe bilayers originate at first-order SOC. Taking the 3m (C3v) torque as a paradigmatic example, we elucidate the role of second- and higher-order SOC torques in field-free switching of perpendicular magnetic anisotropy. Remarkably, in PtMnSb, we demonstrate that SOTs under certain point group symmetries deviate from the conventional form: zeroth- and first-order SOC contributions vanish identically, with the leading SOT emerging at second order. All symmetry-based predictions from spin-group theory are in excellent quantitative agreement with first-principles calculations. Our work establishes a unified symmetry framework for the microscopic understanding of the Edelstein effect and current-induced spin torques in ferromagnetic systems.
